The present invention relates to measuring human/mechanism interfaces, and more particularly to such measuring systems that relate to the measurement of relatively small one degree of freedom mechanisms, such as switches.
As the market for sales of products becomes more competitive, a manufacturer must distinguish its products from the competition. Thus, a product design may require more than providing the proper function—it may also require providing a certain feel or image for the product. For example, a small mechanism, such as a switch, may need to not only perform its function of adjusting the operation of a product, but also provide a certain feel to the switch operator while being actuated. Such a switch feel may give an impression of quality or distinctiveness to the product, and one may wish to have this particular feel for all of the switches on a given product—that is, a switch feel harmony. Thus, the feel of a switch may be almost as important as the function the switch performs. In order to define and achieve this feel, the human/machine interface for that particular switch must be defined.
In addition, for many manufacturers, the switches are fabricated by multiple suppliers. In order to maintain switch feel harmony, then, one must be able to not only define the switch feel characteristics in a quantitative and objective manner, but also posses an ability to measure the switches produced by the suppliers, in an accurate and reliable way, in order to verify that the switches meet the criteria. Consequently, an accurate and repeatable way to define and measure switches is needed.
Conventionally, measurements for determining characteristics of switches were accomplished by mounting the switches in laboratory type fixtures and connecting them to a switch measurement device. Typically, these measurement devices measured the peak force that was applied during switch actuation and possibly also the range of motion. But peak force alone cannot completely define the human perception of feel. Two switches having the same peak force can feel quite differently. Consequently, the feel of such switches was determined by consensus in panel studies. These conventional approaches, however, do not produce a quantitative, objective, verifiable, and repeatable means for completely measuring the feel of a switch.
As a result, some of the more advanced systems employ a laboratory type fixture with a more advanced measurement device that can measure the force applied to the switch as the switch moves through its range of motion. This force/displacement profile, then, provides a more complete definition of the switch properties.
For switches that pivot, the switch measurement system must be able to properly grip and/or contact the switch while manipulating the switch about its pivot axis. In the past, however, measurement systems have used linear measurements for pivot switches, which inherently introduces error into the measurements since pivot switches move in an arc, not a straight line. Moreover, to precisely and repeatably measure the torque/angular displacement characteristics of pivot switches, an accurate alignment of the axis of the switch measurement unit with the pivot switch being measured is required. Merely a rough visual alignment will generally yield inconsistent and less accurate results than is desired for defining and verifying the switch feel characteristics of a pivot switch.